Steering wheel heating devices that detect a region of a steering wheel touched by a person and warm the detected region with a heater have been conventionally proposed. FIG. 14 is a block diagram illustrating the structure of a steering wheel heating device of a vehicle disclosed in Patent Literature (PTL) 1. FIG. 15 is a plan view illustrating the appearance of a steering wheel.
In FIG. 14, the steering wheel heating device includes a microcomputer (hereafter referred to as “CPU”) 101, a hold detection unit 102, a 0.1 sec timer 103, an input buffer 104, a power unit 105, a temperature control 106, a bimetal switch 107, a heat wire 108, a relay driver 109, relays 111, 112, 113, and 114, switches 115 and 116, and four heaters 117, 118, 119, and 120.
In a steering wheel 121 in FIG. 15, the heaters 117, 118, 119, and 120 are respectively installed in regions 122, 123, 124, and 125 formed by dividing the circumference into quarters.
In the case where the switch 115 is in the “auto” position, for example, the CPU 101 turns on the relay 111 when detecting the driver's hold in the region 122 of the steering wheel 121, and turns on the relay 112 when detecting the driver's hold in the region 123 of the steering wheel 121. In detail, when the driver holds the part of the region 122 of the steering wheel 121, the heater 117 is energized to warm the region 122. When the driver holds the part of the region 123 of the steering wheel 121, the heater 118 is energized to warm the region 123. Since only the heater of the region held by the driver's hand is energized in the steering wheel heating device, the steering wheel 121 is warmed efficiently.